The present invention relates to a linear motor. More specifically, the invention relates to a linear motor that uses a claw pole type yoke unit.
Japanese Patent Application Laid-Open Publication No. 160348/1989 discloses a linear motor including a stator constituted by an armature unit and a movable element constituted by a permanent magnet row unit. The armature unit includes a coil made of annularly winding conductors and claw pole type yoke units arranged for the coil. The coil includes a pair of linear portions and a pair of coupling portions. The pair of linear portions extend linearly and face each other with a spacing therebetween. The pair of coupling portions connect the pair of linear portions. Each of the claw pole type yoke unit includes a plurality of first pole teeth, a plurality of second pole teeth, and a yoke. The first pole teeth extend in one direction and are arranged to form a row along the linear portions of the coil. The second pole teeth extend in the other direction opposite to the one direction and are arranged to form a row along the linear portions of the coil. The yoke magnetically couples the first pole teeth to the second pole teeth. Each of the claw pole type yoke units is arranged so that the first pole teeth and the second pole teeth are exposed toward an outside of the coil. The permanent magnet row unit includes a permanent magnet row formed by a row of a plurality of permanent magnets and a back yoke made of a magnetic material, for supporting the permanent magnet row in a state where this permanent magnet row is arranged in parallel. Then, the permanent magnet row unit is arranged adjacent to the coil so that magnetic pole surfaces of the permanent magnet row face the first and second pole teeth of the claw pole type yoke units.
In the linear motor of this type, it is required to reduce thickness of the linear motor in a direction orthogonal to a moving direction of the movable element. However, in the conventional linear motor, reduction of the thickness is limited. Further, in the conventional linear motor, the back yoke made of the magnetic material must be used for the permanent magnet row. Further, an allowable load of a bearing with a small thickness is small. Thus, life of the bearing is reduced due to a magnetic attraction force of the linear motor.